Prototroctes modestus Schwarzhans, 2012

Schwarzhans, Werner, Scofield, R. Paul, Tennyson, Alan J. D., Worthy, Jennifer P. & Worthy, Trevor H., 2012, Fish remains, mostly otoliths, from the non-marine early Miocene of Otago, New Zealand, Acta Palaeontologica Polonica 57 (2), pp. 319-350 : 332

Prototroctes modestus Schwarzhans sp. nov.

Fig. 7C–H.

Etymology: From Latin modestus , modest, referring to the inconspicuous outline of the otolith.

Type material: Holotype: NMNZ S.52726 ( Fig. 7C) . Paratypes: 16 specimens (15 specimens NMNZ S.52727, same location as holotype; 1 specimen NMNZ S.52728, Wharekuri Creek near Aviemore, Otago, early Miocene , Bannockburn Formation ) ( Fig. 7D–H) .

Type locality: Home Hills Station, Manuherikia River near St Bathans , Otago .

Type horizon: HH1a bed, Bannockburn Formation, early Miocene.

Diagnosis.—Thin otoliths with compressed outline and regularly rounded ventral rim. OL:OH = 0.95–1.05. Dorsal rim without postdorsal indentation.

Description.—Compressed, thin otoliths with broadly rounded ventral rim. Size up to 2.5 mm. Rostrum massive, pointed, moderately long; excisura narrow, not deep; antirostrum short. Posterior rim broadly rounded, somewhat oblate postdorsally. Dorsal rim short, high, highest behind midpoint. Rims smooth or delicately crenulated. OH:OT = 3.7–3.8.

Inner face markedly convex, with long, narrow, deepened, slightly supramedian sulcus. Ostium as narrow as cauda, very short, anteriorly open; cauda slightly swinging, terminating close to posterior rim of otolith, with ventrally pointed tip. OL:SuL about 1.1; CaL:OsL = 2.0–2.5. Dorsal field small, with small, ventrally well marked depression. Ventral field wide, smooth, with faint ventral furrow moderately close to ventral rim.

Outer face flat to slightly concave, rather smooth.

Remarks.—Of the two species of the genus recorded here in the Bannockburn Formation, P. modestus is less common, the other being P. vertex Schwarzhans sp. nov. (see below for differentiation). Otoliths of P. modestus closely resemble those of the Recent P. maraena Günther, 1864 ( Fig. 7A) from southern Australia, except for the more deeply and gently curved ventral rim and the different proportions of the dorsal rim. Otoliths of the recently extinct P. oxyrhynchus Günther, 1870 from New Zealand are not known. Otoliths of Retropinna semoni (Weber, 1895) ( Fig. 7B), representing the other Recent genus of the family, are smaller, like the fishes themselves, and show a straight cauda with a rounded tip (versus swinging cauda with a ventrally pointed tip).

Stratigraphic and geographic range.—Bannockburn Formation, Manuherikia River and Wharekuri Creek.